Study of healthy preterm infants affords an opportunity to investigate the contributions of visual experience vs. preprogrammed mechanisms on visual development. By comparing the developmental trajectories of contrast sensitivity (CS) in preterm vs. fullterm infants, we can determine if development is primarily tied to postterm age, in which visual maturation is governed by preprogrammed mechanisms timed to conception. By contrast, if development is tied to postnatal age, then visual maturation may be affected by visual experience. Using forced-choice preferential looking methods, data from 57 preterm (born 5-9 weeks early) and 97 fullterm infants were collected between 1-6 months postterm age (2-7 month postnatal age). Our visual measures were luminance (light/dark) and chromatic (red/green) CS, which are thought to be mediated by the Magnocellular and Parvocellular subcortical pathways, respectively. In the first few months, luminance CS was found to be predicted by postterm age, suggesting that preprogrammed development is sufficient to account for luminance CS. By contrast, chromatic CS significantly exceeded that predicted by postterm age, which suggests that time since birth (and by extension, visual experience) confers a benefit on chromatic CS. In sum, early Parvocellular pathway development appears to be more influenced by early postnatal visual experience than Magnocellular pathway development. We will present results comparing preterm infants born at different gestational ages, to determine if the slope of postnatal development changes with gestational length at birth. Finally, data will be compared to very preterm infants with retinopathy of prematurity.